1. Field of the Invention
The field of this invention is hearing protection, specifically in high noise environments where effective communications may also be needed.
2. Description of Related Art
There are numerous earplug devices currently patented, the majority of which are mass-produced designs based on soft elastomers or foam materials. They are placed in the ear canal and occupy positions up to but not generally past the second bend of the ear canal. Custom fitted ear plugs have also been designed and are commercially available as soft solid silicone plugs which are placed in the concha and outer ear canal, and as hard shell devices such as those described by Haussmann (U.S. Pat. No. 7,025,061) that reside in the same area. Recently, deep insertion custom solid silicone earplugs which extend through the second bend of the ear canal have been tested by the armed forces. These devices have been found to produce superior attenuation to other types due to their deep insertion up to and sometimes past the second bend of the ear canal (although comfort is an issue).
Virtually all custom hearing protectors have been designed and fabricated using the same technologies that are used to create hearing aids. For this reason, a brief discussion of hearing aids is useful. All hearing aids receive sound via a microphone, amplify the signal produced, and then drive a speaker which is configured so that the sound produced is directed to the eardrum. There are a number of hearing aid types. Accepted industry type names include “In-The-Ear” (ITE), “In-the-canal” (ITC), “Completely-In-Canal” (CIC), and “Behind-the-Ear” (BTE). Each device name denotes a distinct and broadly accepted definition of geometry. ITE devices fit in the outer ear concha and extend only minimally into the ear canal. These devices are visible looking into the ear, and often visible when facing the person from the front. ITC devices are smaller, and fill only the innermost portion of the external ear, and the outermost portion of the ear canal and opening of the canal. They are visible looking into the ear, but very little from the front. CIC devices are generally fitted deep into the ear canal and may be invisible altogether even when looking into the ear. BTE devices are large curved devices that fit behind the ear and provide a sound tube which passes over the top of the ear and into the ear canal where an eartip is located. ITE, CIC, and ITC hearing aids typically use hollow shells with the electronics and transducers fitted inside them. In addition, special molds have been used to produce solid plugs, and soft flexible hearing aids as well as earmolds for BTE hearing aids.
The primary difference between a hearing device that is a hearing aid and a device that is a hearing protector lies in the differing goals of amplification vs. attenuation. The technologies used to create custom devices of either type are similar and share many common elements. Both types of devices begin by acquiring an impression of the outer ear and ear canal where the device is intended to reside. This is typically done by injecting a fast curing material into the ear canal and concha. This impression can be processed into a device using the traditional invest and cast methods which are widely described in the literature, or using a digital approach wherein the impression is converted into a 3D mathematical representation, often by using a laser scanner, and manipulated to become a device design using various specialized software packages. The device or a set of molds for the device are then created using 3D printing, also known as Rapid Prototyping. These systems employ Stereolithography (SLA), Selective laser Sintering (SLS), jet droplet deposition, or other methods. In the case of hard earshell based devices, the shell can be printed directly from an otoplastic. In the case of a cast device, the mold may be printed directly, and the device material cast into it. Once cured, the mold is removed.